The Perfect Marriage of Great Science and Great Hair
November 7, 2007 7:24 AM   Subscribe

A 2007 Nobel Prize-winning breakthrough in genetics may hold the key to eliminating Trichotillomania: the gene Hoxb8 governs grooming behavior in mammals.
posted by hermitosis (12 comments total) 9 users marked this as a favorite
Mice have a gene called hawksbait? That's cool.
posted by kuujjuarapik at 7:45 AM on November 7, 2007 [3 favorites]

Hey, you've got a little something on your shirt there... No, over more... down, down.... Oh, here just let me get that for you. Ahh, that's better.
posted by Horace Rumpole at 8:17 AM on November 7, 2007

Thats a hox gene!? Strange...

I wonder how such a conserved set of genes present in all of animalia can be linked to behavior (do fruit flies excessively groom when this is knocked out to?)
posted by rosswald at 8:23 AM on November 7, 2007

I don't know about fruit flies, but I'd be interested to see if the hox mutation is also the cause of parrots that overgroom and pluck out their feathers.
posted by rmless at 9:27 AM on November 7, 2007

This is a hox.
posted by DU at 9:31 AM on November 7, 2007

I can't wait to see how this turns out! *bites nails*
posted by Ambrosia Voyeur at 10:00 AM on November 7, 2007

But... but... genes are not responsible for behavior?!? I swear. I read it on Metafilter.
posted by tkchrist at 10:23 AM on November 7, 2007

The reason he won the Nobel was because knockout mice can be used to help determine the function of *any* gene-- so the implications of his research go well beyond trichotillomania.

And now we have conditional knockout mice-- where you can turn a gene on or off after birth, so the ones that are lethal if knocked out during development can be see in action in adults (and so you can distinguish between a gene product's role in development and its role in adults, which is very important in neuroscience)-- and "knockin" mice where, I believe but could be wrong, you add a gene rather than deleting one.
posted by Maias at 12:32 PM on November 7, 2007 [1 favorite]

Thank you, Maias. I came across the info in researching trich so that wound up being the angle I took, but I am equally interested to see what else they uncover. It sounds near-limitless in its uses.

Also, the phrase "conditional knockout mice" is amazing. Sort of eerily close to "teenage mutant ninja turtles".
posted by hermitosis at 1:23 PM on November 7, 2007

I think a strong case has been made that built-in grooming behavior in animals has been selected for by problems with mite and insect infestation; for us hairy mammals, lice which hide in our hair and glue their eggs (nits) to the shafts of our hairs near the skin are a special problem.

Trichotillomania, therefore, which involves pulling hair shafts between fingernails and fingers (removing some of the nits and adults) and pulling hair out altogether (also removing nits and removing cover) can be seen as a built-in behavior 'designed' to cope with lice.

There are all kinds of problems associated with performing this behavior except when needed, so it's reasonable to search around for things which might be associated with such infestation and could turn the behavior on-- presumably by activating hoxb8 and other genes as well as other modalities.

I think some recent research points to something which could be a major factor in switching trichotillomania on. It turns out that people with chronic, refractory to treatment sinusitis have a gene which is about 250 times as active as in normal controls: the gene for chitinase.

Chitinase is an enzyme which dissolves chitin, and chitin is one of the major components of the cell walls of the larvae of insects and the exoskeletons of adult insects, the shells of shellfish such as lobster and even squid, the cell walls of fungi, including mushrooms and yeasts (don't forget mold spores, the beaks of octopi, shells of molluscs like oysters, and the skins of parasitic roundworms. It is a polysaccharide, not a protein. Previous studies have linked chitinase and asthma. The authors of the study describe this increase in gene activity as a response to 'ghost parasites':

The theory, Lane says, is that allergies and asthma result from genes that control the body's defenses against parasites, but these genes are dormant in healthy people. However, when turned on by so-called ghost parasites, the potent inflammatory response is medically very difficult to control.

However, in modern times, chitin is found in many more places than those listed. Chitin and chitosan, a digested and solubilized byproduct of chitin, have become extremely important industrial, medical, and food technology materials:

Chitin is used in water purification, and as an additive to thicken and stabilize foods and pharmaceuticals. Chitin also acts as a binder in dyes, fabrics, and adhesives. Industrial separation membranes and ion-exchange resins can be made from chitin. Processes to size and strengthen paper employ chitin.

Chitin and chitosan are also extensively used in cosmetics, such as hair fixers and shampoos, some of which owe the set or shine they impart to hair to chitin or chitosan.

Note that some of the things which contain chitin and chitosan, such as shellfish and mushrooms, often appear on lists of foods to be avoided by trichotillomaniacs, and others, such as the shampoos, lotions, cosmetics and food with chitosan in them (not to mention mold spores) can scarcely be avoided by anyone.

In short, I'd guess that the same things which activate the gene for chitinase will turn out to activate hoxb8 if it is indeed the gene for trichotillomania, and that these will include many common foods, food and cosmetic additives, and particles in the air we breathe, all because of their chitin or chitosan content and its association with insects.
posted by jamjam at 1:28 PM on November 7, 2007 [2 favorites]

jamjam, are you saying that my body's reaction to chitin and chitosan (atmospheric or consumed) might be triggering trich behavior? Amazing. Also, allergies and asthma certainly run in my family.

Are there ties between delusional parasitosis and trichotillomania?

This is all incredibly fascinating. I can remember having trich to a lesser, unproblematic degree when I was a teenager, but recently my mother told me that I used to do the same thing when I was a child. While my condition is aggravated by stress and other personal factors, the genetic theory makes a lot of sense to me because of this childhood activity. The idea that it could be linked to diet, cosmetics, and atmosphere is something I'd never considered-- consider my mind blown.
posted by hermitosis at 1:43 PM on November 7, 2007

I obsessively pick at my scalp, is this related to trich?

And hear I thought it was all psychological, it amazes me that there may be genetic behavior involved. Of course, it all makes sense.
posted by symbioid at 2:23 PM on November 7, 2007

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